| The colorful pseudoscience|
|Hating thy neighbour|
|Divide and conquer|
Hereditarianism (aka Jensenism) is a racist pseudoscience that argues mean differences in IQ between human populations (socially constructed races and ethnic groups) are significantly the result of genetics. Proponents of hereditarianism typically argue (following Jensen, 1973) that the black-white IQ gap is caused by 50% to 75% genetic factors (although some argue as high as 80% to 100%) while 25% to 50% environmental factors.
As mentioned by Linda Gottfredson (2005):
“”Rushton and Jensen's (2005) hereditarian hypothesis is that Black-White differences in general intelligence (IQ, or the general mental ability factor, g) are "substantially" genetic in origin.
- 1 History
- 2 Black-white IQ gap
- 3 Racialism
- 4 Racism
- 5 Heritability of IQ
- 6 Rindermann et al. surveys
- 7 Arguments against hereditarianism
- 8 References
Probably the first argument for hereditarianism was made in 1869 by Francis Galton who used scores on mathematical and civil-service tests instead of IQs, and used ancestral lineages of the subjects to measure proximity to "great" men. Galton also coined the term "eugenics". In the early 20th century, before IQ tests were popular (although sometimes used) racists made different arguments to establish a racial hierarchy in intelligence e.g. the pseudoscientific theory intelligence is correlated to brain size, with whites having the average largest brains and blacks the smallest. This was falsified by Franz Boas (1938) who showed that Eskimos have the largest mean brain-sizes, without asserting their superiority. While it is true cranial capacity on average slightly differs by ethnic group, Beals et al. (1984) found smaller cranial capacities are found in warmer climates, while larger in colder; the variation in brain-size between populations is caused by natural selection. There's also some evidence that brain size correlates moderately with intelligence: a 2005 meta-analysis found a correlation of r=0.33, implying that brain size explains about 0.33*0.33=11% of the variation in intelligence. But more recent evidence suggests that this and other previous estimates of the brain size-intelligence relationship were inflated, and that the actual relationship is much weaker. Accordingly, "it is not warranted to interpret brain size as an isomorphic proxy of human intelligence differences."
In 1958 Audrey M. Shuey published The Testing of Negro Intelligence; by this time the use of IQ and other standardized tests of intelligence had become politicized by segregationists as a backlash against the Brown v. Board of Education (1954) decision to desegregate public schools. Shuey argued the black-white IQ gap is largely the result of genetic factors to justify racial segregation. However, Pettigrew (1964) reported he was able to find only three American psychologists (including Shuey and her PhD supervisor, Henry Garrett, a segregationist) out of 21,000 members of the American Psychological Association, who were hereditarians. This is likely because it was not until 1968 that all forms of segregation had been declared unconstitutional by the Supreme Court and most racists wouldn't have become interested in hereditarianism until segregation had formally ended.
In 1969, the psychologist Arthur Jensen (1923–2012) published a controversial paper "How Much Can We Boost IQ and Scholastic Achievement" in Harvard Educational Review suggesting genetic factors are "strongly implicated" in average group differences in IQ between blacks and whites:
So all we are left with are various lines of evidence, no one of which is definitive alone, but which, viewed all together, make it a not unreasonable hypothesis that genetic factors are strongly implicated in the average Negro-white intelligence difference. The preponderance of the evidence is, in my opinion, less consistent with a strictly environmental hypothesis than with a genetic hypothesis, which, of course, does not exclude the influence of environment or its interaction with genetic factors.
This view became known as Jensenism based on the idea mean differences in IQ between populations have high between-group heritability. Some contemporary hereditarians include: Richard Lynn, Helmuth Nyborg, Emil Kirkegaard, Gerhard Meisenberg, Heiner Rindermann, Michael A. Woodley of Menie, Paul Irwing, Adam Perkins, Davide Piffer, Roger Pearson, John Fuerst, James Thompson, David Becker, Jared Taylor, Peter Frost, Frank Ellis, Michael Levin, Kenya Kura, Jan te Nijenhuis, Noah Carl, Edward Dutton, Fróði Debes, Stefan Molyneux, Gregory Cochran, Nicholas Wade, Guy Madison, Linda Gottfredson, Seymour Itzkoff, Frank Miele, Richard Haier, Edward M. Miller, Kevin MacDonald, Andrew Sabisky, Satoshi Kanazawa, Neven Sesardić, James Watson, Aurelio J. Figueredo and Dimitri van der Linden. Many of these individuals have published in the white supremacist journal Mankind Quarterly and OpenPsych pseudojournals, while nearly all of them are known to have right-wing to far-right/alt-right political beliefs. According to Snyderman & Rothman (1988) individuals with traditional conservative political views are "more likely than liberals to believe that genes play a causal role in race and class differences in IQ".
In 1973, 341 American Psychological Association members were asked whether they disagreed or agreed with Jensen's statement (quoted above). The survey revealed 60% disagreed, compared to only 28% who agreed and 2% unsure. There is therefore scientific consensus against hereditarianism despite claims to the contrary by hereditarians.
The Bell Curve
The controversy over race and IQ culminated in 1994 with the publication of The Bell Curve.
Black-white IQ gap
The black-white IQ gap refers to the mean IQ difference between self-identified black and white Americans that hereditarians claim is 15 IQ points (e.g. Jensen, 1969). However, Turkenheimer et al. 2017 argue the 15 point gap is historical, and that the gap has been substantially narrowed in the last few decades; the difference is now 9.5 IQ points:
...it is almost surely the case that the black-white IQ gap has been very substantially reduced. (The race gap in IQ itself has not to our knowledge been investigated since 2006, when Dickens and Flynn found that it was around 9.5 points, close to what is suggested by Reardon’s achievement data.)
In other words, the mean IQ of black Americans has risen from 85 to 89-90; the mean IQ of white Americans is about 100.
Most racialists who nowadays call themselves "race realists" are proponents of hereditarianism. The exception includes a small number of academics who argue for the existence of human races, but maintain the black-white IQ gap has zero or a trivially small genetic basis e.g. Michael O. Hardimon who defends a minimalist concept of races "characterized by nothing more than outward physical differences and health-related biological susceptibilities." Spencer (2014) argues for a similar biological race definition, and states his theory in terms of genetics "does not entail that there are aesthetic, intellectual, or moral differences among races." The pioneer of racialist non-hereditarianism was Theodosius Dobzhansky, who was an outspoken proponent of the idea human races exist, but published a paper criticizing Jensen's hereditarianism hypothesis, argued for race equality, and in his book Genetic Diversity and Human Equality (1973) also rejected hereditarianism, given the lack of evidence and reality environmental factors most likely explain the black-white IQ gap.
Because non-hereditarianism is a minority viewpoint within racialism and hereditarianism is racist, Hardimon (2017) re-labels himself as a minimalist race proponent opposed to a racialist to avoid the negative connotations or harmful affect of racialism: "The minimalist concept of race provides a nonmalific alternative to the racialist concept of race". Non-hereditarianist racialism while more reasonable than hereditarianism because it rejects racism and white supremacism, is still a pseudoscience since human races don't exist as biological constructs, but are social constructs, e.g. some ethnic groups considered to be "white" today weren't a century ago (see definitions of whiteness in the United States).
Hereditarians view racial inequality in IQ as predominantly genetic, rather than largely or entirely the product of socioeconomic environmental factors and hence argue "equalizing opportunities cannot, in fact, remove black/white disparities in IQ" because of a natural race hierarchy in intelligence. This is obviously racist, and proponents of hereditarianism often describe anti-hereditarians as "egalitarians", e.g. according to J. Philippe Rushton (1995) it is a "politically correct equalitarian fiction" that "races are genetically equal in cognitive ability".
“”If my work was motivated by racism, why would I want Asians to have bigger brains than whites?
|—J. Philippe Rushton|
Hereditarianism in the early 20th century was explicitly white supremacist with whites at the top of the IQ pyramid, East Asians in the middle, and blacks as the bottom. However, in the late 20th century Richard Lynn, J. Philippe Rushton and several other hereditarians began to change the racial hierarchy, placing East Asians at the top of the pyramid. Whereas early 20th century hereditarians also argued whites have the largest brains, Rushton would now argue Asians do. Contemporary hereditarians try to silence their critics and deny being racist by pointing out they cannot be white supremacists if they're arguing East Asians on average are smarter than whites. However, this is widely considered a ploy to deflect charges of racism, while at the same time maintaining blacks are mentally inferior; after all, even in the revised pyramid, blacks are still placed at the bottom by hereditarians:
“”Reversing the order of the ﬁrst two races was not a strategic loss to raciocranial hereditarianism, since the major function of racial hierarchies is justifying the misery and lesser rights and opportunities of those at the bottom.
“”European racially oriented researchers can now deﬂect charges of racism or ethnocentrism by pointing out that they no longer place themselves at the top... this shift does not affect the major focus of many ideas regarding racial superiority that continue to place people of recent African descent at the bottom.
“”Of course the real point of the argument is not to show how smart Mongoloids are, but to provide scientific sounding proof of the innate inferiority of Negroids.
Despite hereditarians putting East Asians at the top of the IQ pyramid, there are still white supremacist arguments, e.g. the hereditarian James Thompson cites a pseudoscience talk presented at the London Conference on Intelligence that maintains "Asians are bright, but not curious" and Lynn (2008) states "North East Asians have a higher IQ than Europeans, but their creative achievements have been less." Hereditarians argue that while East Asians have higher IQ's than whites, they're far less creative and inventive.
Heritability of IQ
Heritability is a statistical concept (H/h²) that describes how much of the variation in a trait or character within a population is caused by genes. However, this should not be confused with cause per se, e.g. a trait might be under strong genetic control, but has 0 heritability because there is no variation, for example everyone is born with two legs:
And yet walking on two legs is clearly a fundamental property of being human, and is one of the more obvious biological differences between humans and other great apes such as chimpanzees or gorillas. It obviously depends heavily on genes, despite having an estimated heritability of zero.
While there are no conclusively-identified genes that affect human intelligence, some research, such as that of geneticists Robert Plomin and John DeFries, propose that the heritability of IQ in human populations is around .50. However, this says absolutely nothing about the cause of IQ group differences between populations; broad-sense heritability is formally defined as the proportion of phenotypic variation (VP) within a population due to variation in genetic values (VG) and should not be confused with between-group heritability. Stephen Jay Gould (1980) cautioned not to confuse the two:
The value of heritability within either the white or black population carries no implication whatever about the cases for different average IQ between two populations. A group of very short people may have heritability's for height well above 0.9, but still owe their relative stature entirely to poor nutrition. Within and between group variation are entirely different phenomena; this is a lesson taught in any basic genetics course.
Lewontin (1970) and Loehlin (1992) provide a useful thought experiment in plant genetics, i.e. two populations of corn have extremely high heritability for a trait, but mean group differences between them are entirely caused by environmental rather than genetic factors; therefore between-group heritability is zero, despite within group heritability nearly 100%:
Suppose two handfuls are taken from a sack containing a genetically diverse variety of corn, and each grown under carefully controlled and standardized conditions, except that one batch is lacking in certain nutrients that are supplied to the other. After several weeks, the plants are measured. There is variability of growth within each batch, due to the genetic variability of the corn. Given that the growing conditions are closely controlled, nearly all the variation in the height of the plants within a batch will be due to differences in their genes. Thus, within populations, heritabilities will be very high. Nevertheless, the difference between the two groups is due entirely to an environmental factor—differential nutrition. Lewontin (1970) didn't go so far as to have the one set of pots painted white and the other set black, but you get the idea. The point of the example, in any case, is that the causes of between-group differences may in principle be quite different from the causes of within-group variation.
Jensen's straw man
Proponents of hereditarianism such as Jensen (1970, 1973) and Jensen & Rushton (2005) have always acknowledged the aforementioned difficulty, but argue that if two or more populations share a high heritability for a trait or character, it increases probability that average group differences are caused by genes and between-group heritability is above 0:
The real question is not whether a heritability estimate, by its mathematical logic, can prove the existence of a genetic difference between two groups, but whether there is any probabilistic connection between the magnitude of the heritability and the magnitude of the group differences. Given two populations (A and B) whose means on a particular characteristic differ by x amount, and given the heritability (hA2 and hB2) of the characteristic in each of the two populations, the probability that the two populations differ from each other genotypically as well as phenotypically is some monotonically increasing function of the magnitudes of hA2 and hB2.
“”High within-group heritability cannot prove between-group heritability, but it does increase the a priori likelihood of finding genetic components in the average difference between groups.
|—Jensen, A. R. (1973). Educability and Group Differences. Routledge. p. 356.|
The cause of individual differences within groups has no necessary implication for the cause of the average difference between groups. A high heritability within one group does not mean that the average difference between it and another group is due to genetic differences, even if the heritability is high in both groups. However, within-groups evidence does imply the plausibility of the between groups differences being due to the same factors, genetic or environmental. If variations in level of education or nutrition or genes reliably predict individual variation within Black and within White groups, then it would be reasonable to consider these variables to explain the differences between Blacks and Whites.
This argument from mathematical logic has been criticized for lack of empirical support. While it may be theoretically true, it has never been demonstrated in any test. Jensen also never tried to quantify an estimate for between-group heritability from this argument and only ever claimed high within-group heritability is evidence for non-zero between-group heritability, supporting hereditarianism. This is arguably a straw man since almost all scientists are not against the possibility group differences in IQ are negligibly (1-5%) caused by genes, which is above zero, but most these scientists are against hereditarianism. Earl Hunt former president of the International Society for Intelligence Research thus noted:
“”Many researchers who are primarily interested in environmental differences associated with racial and ethnic differences in intelligence would not be at all perturbed by an ironclad demonstration that, say, 3% of the [black-white] gap is due to genetic differences.
|—Human Intelligence. (2010). Cambridge University Press. pp. 434-435.|
Gould (1994) for example in his critical review of The Bell Curve didn't rule out the possibility that genes play a very minor role in average group differences in IQ: "the strong circumstantial case for substantial [environmental] malleability and little average genetic difference" (emphasis added). Similarly, Nisbett (2005) who published a paper heavily criticizing Jensen & Rushton (2005) doesn't deny the possibility genes are negligibly involved in explaining the black-white IQ gap, i.e. "close to zero" meaning not absolutely nil:
“”On the contrary, the converging methodologies provide strong evidence that the genetic contribution to the Black–White IQ gap is close to zero and do not even suggest a direction for any possible genetic contribution.
|—Richard E. Nisbett, "Heredity, Environment, and Race Differences in IQ"|
Therefore concerning between-group heritability: anti-hereditarians either argue for 0% genes, but accept the possibility of a very small percentage of genes (e.g. Lewontin, 1970; Gould, 1994; Nisbett, 2005) or argue for the latter (Loehlin et al. 1975; Hunt, 2010). Note Jensen defined hereditarianism as the view genetics explains between 50% and 75% of the black-white IQ gap and not a figure close to zero (e.g. 3%), so it's intellectually dishonest to try to redefine hereditarianism to mean, say, 97% environment and only 3% genes:
In view of all the most relevant evidence which I have examined, the most tenable hypothesis, in my judgment, is that genetic, as well as environmental, differences are involved in the average disparity between American Negroes and whites in intelligence and educability, as here defined. All the major facts would seem to be comprehended quite well by the hypothesis that something between one-half and three-fourths of the average IQ difference between American Negroes and whites is attributable to genetic factors, and the remainder to environmental factors and their interaction with the genetic differences.
The hereditarian position originated in the work of Charles Darwin (1859, 1871) and then was elaborated by his cousin Sir Francis Galton (1869, 1883). Based on research models used in behavioural genetics, this view contends that a substantial part (say 50%) of both individual and group differences in human behavioural traits is genetic… a 50% genetic–50% environmental etiology for the hereditarian view…
However, instead of trying to test and demonstrate this, both Jensen and Rushton throughout their careers would focus on trying to falsify zero between-group heritability, that they described as the "only environmental" or "only culture" view. Charles Murray often uses the same straw man and defines hereditarianism as only above-zero between-group heritability to argue "if you say it is likely that there is any genetic component to the black-white difference in test scores, the roof crashes in on you." This is false, since it would mean absurdly classifying anti-hereditarians who accept the possibility or likelihood there is a very minor genetic component involved in the black-white IQ gap, as hereditarians.
Knapp et al. (1996) criticize Murray's use of Jensen's straw man:
In fact, neither characterization [Herrnstein & Murray 1994] is accurate or honest. Theorists such as Lewontin have never denied the possibility of genetic influences; what they have denied is that there is any convincing evidence of any genetic influences.
They also criticize Herrnstein & Murray's (1994) book The Bell Curve for deceptively claiming to be "agnostic" about between-group heritability:
Herrnstein and Murray's 'agnosticism' is a pose.... its function is to lead the reader to entertain the race hypothesis, without requiring Herrnstein and Murray to defend it. However as soon as they turn to the further analysis, their agnosticism and warning that one cannot infer genetic differences promptly vanish.
Herrnstein & Murray (1994) extensively quote and cite Jensen in their work, as well as rely heavily on the pseudoscientific racist theories of J. P. Rushton and Richard Lynn. Laughably, Herrnstein & Murray (1994) defend Rushton, by saying his research on race and intelligence is "not that of a crackpot or bigfoot" and is "plainly science" (p. 667).
Having failed to actually provide any evidence for hereditarianism, Jensen in 1998 argued that hereditarianism should be accepted as the default hypothesis:
On the basis of the present evidence, perhaps the genetic component must be given greater weight and the environmental component correspondingly reduced. In fact, Jensen’s (1998, p. 443) latest statement of the hereditarian model, termed the default hypothesis, is that genetic and cultural factors carry the exact same weight in causing the mean Black–White difference in IQ as they do in causing individual differences in IQ, about 80% genetic–20% environmental by adulthood.
Rindermann et al. surveys
In 2016 Heiner Rindermann and colleagues published a survey on experts opinion of why there are "large differences in cognitive ability and intelligence studies" between cross-national populations. This survey is now quoted by proponents of hereditarianism as proof their view is mainstream. However, the study is flawed for several reasons:
- The survey was emailed to 1345 individuals, but only 265 (20%) responded and just 71 (5%) participated in the survey.
- 14 (20%) survey participants weren't experts, being non-psychologists, including 2 economists (3%) and 1 sociologist (2%).
- The survey acknowledged "one researcher suggested in an email that only politically biased researchers would respond to the questionnaire".
- Some participants had no relevant scientific qualifications at all i.e. the criteria to participate in the survey was to have either published articles in peer-reviewed journals on intelligence/cognitive abilities or have attended intelligence conferences and presented research, e.g. ISIR. The journal Intelligence and ISIR conferences (where the survey was announced) have allowed far-right politically biased individuals such as Emil Kirkegaard to publish articles and present talks, despite being non-scientists with no qualifications.
The survey itself despite these issues and bias, hardly lends support to hereditarianism since it showed that overall "experts attributed about one-sixth to one-fifth of international ability differences to genes (cross-national: 16.99%, single-country: 19.72%)", but that this was "still well below the rated impact of environmental factors (around 50%)." In actual fact if one combines the other non-genetic factors with environmental factors, this equates to around 80% environmental which is the complete opposite of Jensen's default hypothesis of 80% genetic–20% environmental between-group heritability; note Jensen (1973) originally defined hereditarianism as the view genes cause at least 50% of the black-white IQ gap.
Turkenheimer et al. (2017) criticize the survey, noting:
“”Given this very low response rate [5%] along with the potential for bias in which scientists were invited in the first place, we doubt that these results are an accurate representation of the field.
- 0% of differences due to genes: 17% of experts.
- 0-40% of differences due to genes: 42% of experts.
- 50% of differences due to genes: 18% of experts.
- 60-100% of differences due to genes: 39% of experts.
- 100% of differences due to genes: 5% of experts.
The 0% and 100% views reported above are included in the "0-40% of differences due to genes" and "100% of differences due to genes" respectively (since 42% + 18% + 39% = 99% of experts.). This study is quoted by hereditarians who argue it shows their view is mainstream. However, this is erroneous for five reasons: (1) the environmentalist viewpoint was never solely 0% of differences due to genes, since anti-hereditarians have always accepted the possibility genes are negligibly involved (above zero, but close to zero e.g. 3%) in between-group heritability. (2) For this reason clearly more than 17% of experts are anti-hereditarians (3) The largest amount of experts argue for "0-40% of differences due to genes" which is lower than Jensen's threshold of defining hereditarianism as at least 50%. (4) The study suffers from the same bias as the other survey. (5) The survey isn't peer-reviewed. The final results of the survey were published in Intelligence.
Arguments against hereditarianism
The non-validity and non-heritability of IQ
Although most psychologists agree IQ (as a measure of intelligence) has statistical reliability, makes predictions and reliably measures important elements of intelligence a minority of experts argue IQ is invalid and arguably due to competing theories on the nature of intelligence, the concept of IQ itself is still somewhat controversial. One school of thought posits the existence of g-factor or General Intelligence, a single measurable factor underlying all mental activity and various specific factors, specific abilities that come into play in particular kinds of cognitive tasks. Even scientists who agree that G exists don't necessarily agree on its precise nature. There is also the "Multiple intelligence theory" which says that intelligence isn't a single entity and that there are distinct types of intelligence that each exist independently of one another; so if a person exhibits one type of intelligence that doesn't indicate them being high or low on another type. IQ tests are intended to measure the existence of general intelligence.
Hereditarians usually study IQ differences between populations in the sense of broad regions or continents, e.g. J. P. Rushton's Race, Evolution, and Behavior (1995) divides most of the world into three large racial groupings: Caucasoids (Europeans, West Asians, Indians and North Africans), Negroids (Sub-Saharan Africans) and Mongoloids (Northeast and Southeast Asians). This has been criticized on the basis the groupings are arbitrary and useless since they contain populations that have differential mean IQs; Rushton ignored the huge variability within his racial groupings and aggregated populations that are dissimilar. Analysing the mean IQ of populations on a subcontinental level is also inappropriate, for example different countries or ethnic groups in Europe vary on average by up to 12 IQ points. Turkenheimer et al. (2017) discuss the problems with race, and favour instead to analyse average IQ differences between populations at a more local level say Swedes and Greeks, rather than clustering both these ethnic groups into a broader "white" category:
“”Ancestry also allows for more continuous and granular distinctions than our relatively crude categories of race. The ancestry components that geneticists are most commonly including in their analyses are making fine-grained distinctions between people who would all be lumped together as “white” in the US today.
The fact there are self-identified black Americans who have predominantly white American ancestry shows why race is a social, not biological construct. There is also the issue "whiteness" has changed definition; some ethnic groups e.g. Italians who were not considered white in the early 20th century, today are in US political discourse. This is relevant to the black-white IQ gap, since Italians have the highest mean IQ in Europe (102) according to Lynn & Vanhanen (2002) and Lynn (2006). If Italian-Americans are not included as white, this lowers the mean white IQ. Furthermore, in a few cases even ethnic groups by country may be unsuitable population units to analyse average IQ differences since subpopulations (by local city, province or district) may show a disparity in mean IQ scores; this is noticeable among the Han Chinese who differ by up to 7 IQ points depending on China province.
Racial mixture studies
If the black-white IQ gap is significantly due to genes, self-identified black Americans with the most white American ancestry should have average higher IQ scores than those with less white ancestry (genetic studies reveal black Americans range anywhere from between 1% and 98% white American ancestry).6 However studies have repeatedly shown black Americans with predominantly white American ancestry don't have higher average IQs and racial admixture studies fail to support hereditarianism (Nisbett, 2005; Coleman, 2016):
The most directly relevant research concerns degree of European ancestry in the Black population. There is not a shred of evidence in this literature, which draws on studies having a total of ﬁve very different designs, that the gap has a genetic basis.
The first study to use this method (Witty & Jenkins, 1935) focused on 63 children with the highest IQ scores among 8,000 Black American children in the Chicago public school system. When the researchers classified these high-IQ children according to their ancestry as reported by their parents, they found no evidence that they had any more European ancestry than a comparison group of ordinary Black Americans. For example, the results showed that 14.3% of the high-IQ children had predominantly White ancestry, compared to 14.8% of the comparison group. If genetic factors determine the Black–White IQ gap to any significant extent, then there should be substantially more children with predominantly White ancestry in the high-IQ group. In fact, the distribution of White ancestry was remarkably similar in both groups of children, and the brightest child in the entire sample, a girl with an exceptionally high IQ of 200, was one of those whose parents reported no knowledge of any White ancestry at all. This admixture evidence is devastating to the hereditarian interpretation of the Black–White IQ gap… Later studies, using more objective methods for estimating racial admixture and in some cases much larger samples, yielded the same result. Scarr, Pakstis, Katz and Barker (1977) used 43 blood group markers to estimate European ancestry in a sample of 362 Black American schoolchildren in Minnesota and found no significant correlation between European admixture and scores on any of the five separate intelligence tests that they administered. Furthermore, the children with the most European ancestry did not differ significantly from those with the least.
Nisbett (2005) argues adoption studies (e.g. Tizard, 1972; Moore, 1986) are evidence against hereditarianism since they tend to show when middle-class black children are raised by middle-class white families in America or in a highly enriched institutional environment, their average IQs are significantly higher than black children raised by black families.
Lack of evidence
As mentioned, the default hypothesis is the null hypothesis, i.e. zero between-group heritability (0% genes). This has never been falsified. For this reason several scientists e.g. Eric Turkheimer, Richard E. Nisbett argue "there's still no good reason to believe black-white IQ differences are due to genes." Nisbett (2005) however does not deny the possibility genes are negligibly involved in between-group heritability, but sees no reason right now to argue for this since the null hypothesis (0% genes) is the unfalsified default hypothesis.
Significant rises in IQ
Over 14 years (1984-1998), a study found that IQ scores in Kenyan children increased by 11.22 to 26.3 IQ points depending on how test results were converted into IQ, an increase greater than the Flynn effect in developed countries. Since the population essentially remained genetically identical throughout the 14-year period, Daley et al. (2003) proposed that improved healthcare, nutrition, parental literacy, smaller families, and education as explanations. The authors note that parasitic diseases (which cause anemia and thereby reduce intelligence) and malnutrition declined over the 14-year period. Under the 11.22 IQ points per 14 years conclusion, a gain of 24 points could occur over 30 years according to the Flynn effect, assuming that environmental conditions continue to improve. This shows that improvements to the environment can have an appreciable effect on IQ, thereby casting doubt on the use of raw IQ data to prove racial superiority.
Underreporting of African IQ
Lynn and Vanhansen (2006) found that many Subsaharan African countries had IQs in the 60s and 70s. The book was co-authored by Richard Lynn, who has been funded by the Pioneer Fund, and is the source of the colour-coded map of IQ often used by "race realists". Data points used by Lynn and Vanhansen (2006) are not always representative. Hilariously, the IQ of 59 for Equatorial Guinea given by Lynn and Vanhansen (2006) is actually from a study of developmentally-disabled children in Spain. Lynn and Vanhansen (2006) has been criticized by Wicherts et al. (2009) for using lower IQ data points while not including higher IQs (possibly unintentional because they may not have had access to scientific journals from Africa). The report calls below-70 mean IQ figures for Subsaharan Africans "untenable", and estimates a mean IQ of around 81 after correction for methodological issues. The difference between an IQ of sixty-something and an IQ of 81 is important: after correcting for the Flynn effect, the pure-Nordic Danish population in the 1950s would also have had an IQ of around 80. Thus, more realistic estimations of African IQ might permit it to rise to first-world levels through the Flynn effect given sufficient economic development.
- "Introduction to Jensenism". In: C. L. Brace, G. R. Gamble, and J. T. Bond, eds., Race and Intelligence. (1971). Anthropological Studies No. 8. Washington: American Anthropological Association. pp. 4-9.
- Hereditary Genius: An Inquiry into Its Laws and Consequences by Francis Galton (1st ed., 1869; 2nd ed., 1892) hosted at galton.org
- Inquiries into Human Faculty and Its Development by Francis Galton (1883) hosted at galton.org
- “Race,” in General Anthropology edited by Franz Boas, pp. 95–123. New York: D. C. Heath.
- Big-brained people are smarter: A meta-analysis of the relationship between in vivo brain volume and intelligence, Intelligence, Michael A. McDaniel, 2005, 33(4): 337-356
- of associations between human brain volume and intelligence differences: How strong are they and what do they mean?
- Pettigrew, Thoras F., (1964). A Profile of the American Negro. D. Van Nostrand Company: Princeton.
- See Green v. County School Board of New Kent County and Civil Rights Act of 1968
- Jensen, A. R.(1969). "How Much Can We Boost IQ and Scholastic Achievement?". Harvard Educational Review. 39(1): 1–123.
- Snyderman, M., and Rothman, S. (1988). The IQ Controversy, the Media and Public Policy. Transaction Books. p. 134.
- Robert W. Friedrichs, (1973). "The Impact of Social Factors Upon Scientific Judgment: The ‘Jensen Thesis’ as Appraised by Members of the American Psychological Association". Journal of Negro Education. 42: 429-438.
- See Table 3.2 "IQs of Europeans Outside Europe" (USA) in Lynn, R. (2006). Race Differences in Intelligence. Washington Summit Publishers.
- Al-Shawaf, R. (2017). Rethinking Race: The Case for Deflationary Realism by Michael O. Hardimon. The National Book Review.
- Spencer, Q. (2014). "A Radical Solution to the Race Problem". Philosophy of Science. 81(5): 1025-1038.
- Dobzhansky, T. (1973). "Race, Intelligence and Genetics". Psychol. Today. 7(7): 97-101.
- Dobzhansky, T. (1971) 'Race Equality', in R. H. Osborne (ed.) The Biological and Social Meaning of Race (San Francisco: Freeman). pp. 13–24
- Hardimon, M. (2017). "Minimalist Race Concept" in: Zack, N. ed. The Oxford Handbook of Philosophy and Race. Oxford University Press. p. 159.
- J. Philippe Rushton, "The American Dilemma in World Perspective" in Jared Taylor's The Real American Dilemma, 1998, p. 11.
- Quoted in Straightening the Bell Curve, 2012 (Chapter: "The Asian Coefficient"), Constance B. Hilliard
- Lieberman, 2001.
- Relethford, quoted in Lieberman, 2001.
- "A Scientific Approach to Understanding Race and Intelligence" in Race and Intelligence: Separating Science From Myth Jefferson M. Fish ed. (2011) p. 10.
- "Learning Without Questioning – Why Asians do not win Nobel prizes". London Conference on Intelligence, 2014. Kenya Kura.
- Race Differences in Intelligence, Creativity and Creative Achievement.
- Bateson, P., Gluckman, P. (2011). Plasticity, Robustness, Development and Evolution. Cambridge University Press. p. 14.
Plomin and DeFries (1980) reviewed a large body of modern data that jointly indicated that the broad heritability of IQ in contemporary Western populations is around .50, rather than the .75-.80 that Jensen estimated.
- Mackenzie, B. (1984). "Explaining race differences in IQ: The logic, the methodology, and the evidence". American Psychologist. 39(11): 1214-1233, citing: Plomin, R., & DeFries, J. C. (1980). "Genetics and intelligence: Recent data. Intelligence. 4: 15-24.
- Wray, N. & Visscher, P. (2008). Estimating trait heritability. Nature Education.
- Gould, S. J. (1980). "Need for achievement, career and mobility, and the Mexican-American college graduate". Journal of Vocational Behaviour. 16(1): 72-82
- Lewontin, R. C. (1970). "Race and intelligence". Bulletin of the Atomic Scientists. 26 (3): 2–8.
- Loehlin, J. (1992). "On Shonemann on Guttman on Jensen, via Lewontin". Multivariate Behavioural Research. 27(2): 261–263.
- Jensen, A. R. (1970). "Race and the genetics of intelligence: A reply to Lewontin". Bulletin of the Atomic Scientists. 26(5), 1723.
- Jensen & Rushton (2005).
- Mackenzie, B. (1980). "Hypothesized genetic racial differences in IQ: A criticism of three proposed lines of evidence". Behaviour Genetics. 10: 225-234.
- Harwood (1976) points out that the geneticists Richard Lewontin, Walter Bodmer and Jerry Hirsch "accept the plausibility (but not likelihood)" of a small genetic component in race differences in IQ; labelling all three as environmentalists (anti-hereditarians). To this list can be added L. L. Cavalli-Sforza; see his article "Intelligence and Race". (1970). Scientific American. 223(4): 19-29.
- Gould, S. J. (1994). Curveball. The New Yorker, November 28.
- Loehlin et al. in Race Differences in Intelligence (1975) are critical of Jensen's hereditarianism, but favour a minor role of genetics in the black-white IQ gap rather than 0%; in their appendix they estimate between-group heritability at 12.5%, although this is tentative and probably an overestimation since they note, between-group heritability is "more easily accommodated in an environmentalist framework" (p. 238) and so a negligible role for genes (1-5%) is more plausible. Earl Hunt in Human Intelligence (2010) rejects both hereditarianism (as 50-75% or 80% genes) and 0% genes; while emphasising environment, he instead favours an "intermediate" position (p. 435); he provides two examples of low percentage estimates, 3% and 5-15%, but cautions evidence to try to quantify the exact % is currently lacking (p. 436).
- Jensen, 1973, p. 363.
- Jensen & Rushton, 2005.
- Jensen, A. R. (1998). The g factor. Westport, CT: Praege. p. 465.
- Jensen & Rushton, 2005.
- The Assault on Equality, Praeger Publishers p. 126
“”Herrnstein and Murray, in The Bell Curve relied heavily on the work of J. Philippe Rushton. Rushton is cited 11 times in the bibliography (it seems that only Lynn and Jensen were cited more often).
—Joseph L. Graves "The Misuse of Life History Theory: J. P. Rushton and the Pseudoscience of Racial Hierarchy" in Race and Intelligence: Separating Science From Myth (2002) p. 58
- Jensen & Rushton, 2005.
- Brace, C. L. "An Anthropological Perspective on "Race" and Intelligence: The Non-Clinal Nature of Human Cognitive Capabilities". Journal of Anthropological Research. 55(2): 245-264.
- Rindermann, H., Becker, D., & Coyle, T. R. (2020). Survey of expert opinion on intelligence: Intelligence research, experts’ background, controversial issues, and the media. Intelligence, 78, 101406. http://doi.org/10.1016/j.intell.2019.101406
- Turkheimer, E. 1990. “Consensus and Controversy About IQ”. Contemporary Psychology. Vol. 35. No. 5: 428-430).
- Lieberman, L. (2001). "How Caucasoids got such big crania and why they shrank: from Morton to Rushton". Current Anthropology. 42: 69-95.
- Richard Lynn and Tatu Vanhanen in their IQ and the Wealth of Nations (2002, pp. 73-80) provide the following national IQ means (bold = lowest and highest): Albania, 90; Belgium, 100; Bulgaria, 93; Croatia, 90; Denmark, 98; Estonia, 97; Finland, 97; France, 98; Germany, 102; Greece, 92; Hungary, 99; Iceland, 98; Ireland, 93; Italy, 102; Macedonia, 93; Malta, 95; Netherlands, 102; Norway, 98; Poland, 99; Portugal, 95; Romania, 94; Slovakia, 96; Spain, 97; Sweden, 101; Switzerland, 101; Ukraine, 96; UK, 100.
“”In his work on Italian Americans, Fred Gardaphe has sketched the changes in the perception of the Italian identity in the United States, a perception that has classfied Italians as non-white, off-white, or white at different times in the twentieth century. In his book Whiteness of a Different Color, Matthew Jacobson documents the non-whiteness of Italian migrants in the United States though newspaper articles published in the late nineteenth and early twentieth centuries.
—Graziella Parati, Migration Italy: The Art of Talking Back in a Destination Culture (2005) University of Toronto Press. p. 26
- Lynn, R., and Cheng, H. (2013). "Differences in intelligence across thirty-one regions of China and their economic and demographic correlates". Intelligence. 41(5): 553-559.
- Mersha, T. B., and Abebe, T. (2015). "Self-reported race/ethnicity in the age of genomic research: its potential impact on understanding health disparities". Hum. Gen. 9(1): 1-15.
- Nisbett, R. E. (2005). "Heredity, environment, and race differences in IQ: a commentary on Rushton and Jensen". (2005). Psychology, Public Policy, and Law. 11: 302–310.
- Colman, A. M. (2016). "Race differences in IQ: Hans Eysenck's contribution to the debate in the light of subsequent research". Personality and Individual Differences. 103, 182-189.
- Tizard, B., Cooperman, A., and Tizard, J. (1972). "Environmental effects on language development: A study of young children in long-stay residential nurseries". Child Development. 43: 342–343.
- Moore, E. G. J. (1986). "Family socialization and the IQ test performance of traditionally and transracially adopted Black children". Development Psychology. 22: 317-326.
- Daley, T. C., Whaley, S. E., Sigman, M. D., Espinosa, M. P., & Neumann, C. (2003). IQ on the Rise: The Flynn Effect in Rural Kenyan Children. Psychological Science, 14(3), 215-219. http://pdfs.semanticscholar.org/d824/d41d360d8660b64b44e5c0067f50725a78a4.pdf
- Wicherts, J. M., et al., A systematic literature review of the average IQ of sub-Saharan Africans, Intelligence (2009), 15-17. doi:10.1016/j.intell.2009.05.002